In circular knitting and stocking knitting machines, the knitting cam in each knitting station can be moved and positioned in height depending on the knitted article to be manufactured. In such embodiments, the knitting cam is positioned by means of an eccentric conductor which is controlled by a motor and which acts, by means of a dragging needle, on a slide which carries the knitting cam in opposition to the action of a spring, which provides that contact is maintained between eccentric conductor and conducted needle. However, the inertia of the moving parts and the response times of the spring are such that a precise and timely response in the positioning of the knitting cam to the command coming from the actuating means is not always ensured.